[PATCH] clocksource: dw_apb_timer_of: support timer-based delay

Jisheng Zhang
2015-11-03T09:45:34Z

Dear Arnd

On Tue, 3 Nov 2015 09:49:32 +0100
Arnd Bergmann wrote:

> On Tuesday 03 November 2015 14:59:40 Jisheng Zhang wrote:
> > > On Monday 02 November 2015 11:03:34 Jisheng Zhang wrote:
> > > > On Fri, 30 Oct 2015 13:42:01 +0100 Arnd Bergmann wrote:
> > > I'd be happier with a solution that keeps the DT describing the hardware
> > > and not the way we expect Linux to use it, and instead has some heuristic
> > > in the selection of the delay timer. At the moment, we purely base this
> > > on the frequency, which as you say is suboptimal.
> > >
> > > One possible way to improve this would be to add an optional 'latency'
> > > property to the DT nodes (or the driver), and use a combination of latency
> > > and resolution to make the decision.
> >
> > Got it. Thanks for the suggestions. The 'latency' here seems a 'rating'
> > similar as the one in clocksource. I will cook a series for review:
> >
> > patch 1 to make register_current_timer_delay() aware of 'rating'
> >
> > patch 2 to set rating of arch timer as 400
> >
> > patch 3 to add timer based delay support to dw_apb_timer whose rating is 300
>
> Ok. Just to make sure I got this right: your plan is to use the existing
> 'rating' setting as a primary indication, and fall back to comparing the
> frequency if the rating is the same?

Yes, this is my plan.

Thanks,
Jisheng